I'd be so sad if one day I'd discover that the people I consider friends for so long are actually entitled and ungrateful. But the worst thing wouldn't be the discovery in itself. It would actually be the fact that there were probably a bunch of signals before that I just decided to ignore.
People change, sometimes for good, sometimes for the bad. And people can, in fact, change dramatically and become unrecognizable, but it is not one day to the other. Is actually a process that takes time. Sometimes people were kinda awful from the beginning, but you didn't notice because it was just little comments that you didn't particularly like, but that weren't that big of a deal to actually condemn them. The actions took over. You started to feel uncomfortable, but probably brushed it off as just a bad day. Till you realize. You realize how awful they are treating you and how, for so long, you thought you were being understanding, only to discover you were actually just allowing this person to mistreat you.
And when you get tired like u/PutridSignature4927 did in this story. There is no coming back. The only solution is "grow apart". Which is just a nicer term for getting out of there. You may try to talk things out, and I would encourage that decision. But the truth is that nothing is going to change. Some people are like that, and we have no choice but to fully accept it and move on.